A recent global report estimated that 44% of pregnancies among the general worldwide population are unintended (90% uncertainty interval 42–48, data collected 2010-2014) . More precise data from the UK suggests that 16% of pregnancies are unplanned, 29% were ambivalent and 55% were planned (see figure) .
In MS, cohort studies have reported an average unplanned pregnancy rate of 10-20% [3-7]. This rate may be higher in some countries; evaluation of a US clinic cohort found that 32% of pregnancies in women with MS were unplanned . (Note: the rate of unplanned pregnancies in the US general population also appears to be higher than that in other developed countries [8,9].)
Many of these unplanned pregnancies occur in patients who are taking MS therapy. Pregnancies have even been reported in phase III clinical trials which require all patients to provide written consent not to become pregnant and to use reliable contraception .
In the view of experts, treatments that have no influence on pregnancy outcomes would be an advantage, as unplanned pregnancies would not be jeopardized .
The pregnancy section of the European Summary of Product Characteristics for interferon beta including BETAFERON refers to a large amount of data (more than 1000 pregnancy outcomes) from interferon beta registries, national registries and post-marketing experience . These data indicate no increased risk of major congenital anomalies after pre-conception exposure or exposure during the first trimester of pregnancy. Experience with exposure during the second and third trimester remains limited, as treatment was likely stopped with confirmed pregnancy. If clinically needed, interferon beta may be considered during pregnancy . This approach is generally reflected in clinical practice guidelines and expert opinion statements advising that interferon beta therapy like BETAFERON may be continued until pregnancy is confirmed [12-19].
The estimated prevalence of planned, ambivalent and unplanned pregnancies in the general population of Britain 
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